What causes an epidemic of malaria?
This chapter describes the factors that can give rise to an epidemic of malaria. Understanding what may have caused the particular epidemic you are concerned with may help to identify particularly vulnerable groups of people or to indicate whether vector control is important now or to prevent future epidemics. The discussion on specific trigger factors is not meant to be complete. We hope this chapter stimulates you to collect and interpret local information, trying to identify what may have caused the particular epidemic in your area. General principles Epidemics occur as a result of disturbances in the existing equilibrium between the rate of infection and the herd immunity14 of a population in a given area. Malaria epidemics do not generally occur in high-transmission areas (other than when there is migration of non-immune persons into these areas) because the populations of these areas develop partial immunity to the disease. It has been shown that continuous exposure to malaria in
